Instrument spring fastening means



Nov. 29, 1960 R. F. EsToPPEY INSTRUMENT SPRING FASTENING MEANS Filed Jan. 29, 1959 ROYDEN F. ESTO/PEV INVENTOR.

INSTRUMENT SPRING FASTENING mms Royden F. Estoppey, Berkeley Heights, NJ., assignor to Daystrom, Incorporated, Murray Hill, N J., a corporation of New Jersey Filed Jan. 29, 1959, Ser. No. 790,013

4 Claims. (Cl. 324-154) This invention relates to an electrical instrument and more particularly to spring fastening arrangements securing a spiral spring to an abutment member.

The moving system of electrical instruments often includes a spiral spring which is fastened to the moving element of the instrument at an end and to a spring abutment at the other end thereof. The spring abutment is usually adjustable by a suitable zero corrector mechanism and, in prior art arrangements, the spiral spring is generally soldered to the spring abutment. The several steps of a soldering process, including tinning, washing and then soldering, require a considerable amount of time, such that the soldering process is relatively expensive, adding to the cost of the completed instrument. With the fastening arrangement of my invention, no soldering is necessary, and the spring and abutment are quickly and inexpensively fastened together. Further, they are easily disassembled, when desired, without damage to any of the parts.

It will be understood that my novel spring fastening arrangement for fastening the end of a spiral spring to an abutment member in an electrical instrument is not limited to use in any particular type of instrument mechanism. In the embodiment shown and described hereinbelow, the spring fastening means is utilized in an instrument of the permanent-magnet moving-coil type, however, the fastening arrangement is also suited for use in other type electrical instruments such as, for example, a moving-iron vane mechanism wherein the moving element is an iron vane.

An object of this invention is to provide an improved construction for joining the end of the spiral spring to the spring abutment of an electrical instrument.

An object of this invention is the provision of a helical spring having adjacent spring turns, which spring is slid over the free ends of a spiral spring and spring abutment joining the same together.

An object of this invention is the provision of a spring abutment having a free end extending substantially parallel to the extended free end of a spiral spring and joined thereto by a helical spring.

An object of this invention is the provision of an electrical instrument having a moving system balanced by helical spring members, and means including a helical spring member joining a spiral spring to a spring abutment.

These and other objects and advantages will become apparent from the following description when taken with the accompanying drawings. It will be understood that the drawings are for purposes of illustration and are not intended to be construed as defining the scope or limits of the invention, reference being had for the latter purpose to the appended claims.

In the drawings wherein like reference characters refer to like parts in the several views:

Figure 1 is a fragmentary plan view of an instrument embodying my invention;

2,962,550 Patented Nov. 29, 1960 Figure 2 is a fragmentary sectional view taken essen tially on line 2-2 of Figure 1;

Figure 3 is an enlarged perspective view of the fastening means of my invention, the helical fastening spring being shown broken away for clarity; and

Figure 4 is an enlarged plan view of the helical fastening spring.

Reference is first made to Figures 1 and 2 of the drawings wherein there is shown an instrument comprising a base 11 of insulating material, with an integral abutment 12. The instrument mechanism shown is conventional, being of the permanent magnet-moving coil type that includes a generally U-shaped permanent magnet 13 having pole pieces 14, 14 between which is mounted a coil, or movable element, 1d that rotates through an angle which varies with the magnitude of the coil current. A bolt 17 secures a core 18 and plate 19 to the inner face of the abutment 12. The coil 16 is carried by upper and lower axially aligned staffs that are received in adjustable jewelled bearings. In the interest of simplifying the drawings, only the upper staff 21 and its associated bearing 22 have been shown. An offset pointer 23 fixed to the upper staff 21 moves over a graduated scale 24 on a scale plate 24. The bearing 22 is supported on the upper bridge 26 which, in turn, is mounted upon the abutment 12 by studs 27.

For returning the pointer 23 to zero indication on the scale plate when the coil current is Zero, a spiral spring 23 is provided. The inner end 28a of this spiral spring is secured to an upwardly extending tab on a disc 29 which is secured fast to the staff 21. The outer end of the spiral spring 28 is secured to a spring abutment 31 which is carried by the upper bridge 26 between washers 32 and 33 and maintained thereon by a nut 34 threaded to the upper bearing screw. The abutment 31, which is adapted for limited rotation about the bearing axis, is provided with a lateral extension 31a which is formed with an elongated slot 31h. Any conventional zero corrector mechanism, not shown, which includes a crank pin, or arm, engaging the slot 31b, may be used to pivotally adjust the abutment 31.

Reference is now also made to Figure 3 of the drawings wherein the novel fastening arrangement of my invention for securing the spring 28 to the abutment 31 is shown. The abutment 31 is formed with the usual downwardly turned tongue 31C. Attached to, or integrally formed with, the lower end of the tongue 31e is an angular extension 31d lying in the plane of the spiral spring 28 and extending in the direction of the outer free end of the spring. The spring 28 is preferably made long enough to extend beyond the end of the extension. The height of the extension 31d is made somewhat greater than the spring height, and the free end of the extension is tapered as at 36, 36, reducing the height at the end to the spring height, or less. The spiral spring and abutment are fastened together by a helical wound spring 38, shown in sectional view in Figure 3 and in plan view in Figure 4. It will be noted that the helical spring 38 is of the same type (or identical with) the balance spring weights 38' secured to arms from the pointer 23 for balance of the instrument moving system.

In attaching the spiral spring to the abutment, the outer free end of the spiral spring is placed adjacent the abutment, and the helical fastening spring 38 pushed over the spiral spring end and into abutting relation with the tapered abutment end. The helical fastening spring is then turned on up to the bend, designated 31f, in the abutment extension 31d. As will be understood by those skilled in this art, a suitable wrench of the type used to turn the spring balance Weights 38 on the pointer arms the fastening spring 38 is turnedfon upto the said bend.`

With this construction, the spiraispring 28"'is irmly secured to the abutment up to the point that vthe spiralspring and abutment diverge. Hence, the eiective free end of the spiral spring 28 is fixed with respect to the abutment 31.

The cost of attaching the outer spring end to the abutment vwith my novel fastening arrangement'iis substantiallyreduced;from` the costseinvolved in soldering the two together by prior art methods and,'further, the spring 28 is easily'removed without damage to any of the parts when` repair ofthe instrumentnecessitates such removal.

As in the soldered vspring and abutment construction of prior art arrangements, electrical connection to the moving coilY 16 may be made through the spring 2S and abutmentl. The electrical connection provided by the helical fastening spring 38 may have a relatively higher electrical resistanceY than a soldered connection.. Thus, it is preferable to use the spring fastening arrangement in instruments'which themselves have a,relatively high resistance, such'as voltmeters, or in instruments of the type wherein the'resistance is of no consequence, such as milliammeters, etc. As mentioned above, however, theV spring fastening arrangement is not limited to moving coil type instruments wherein the instrument moving element isa coil to which current is fed, but may be utilized in any instrument which includes a connected spiral springfand spring abutment member. Thus, the fastening device may be used in moving iron-vane type instruments, for example, wherein no current is conducted through the spiral spring.

Having` now described my invention in detail, in accordance with the patent statutes, various changes and modi- 4 catons will suggest themselves to those skilled in this art, and it is intended that such changes and modiiications shall fall within the spirit and scope of the invention as recited in the following claims.

I claim:

l. In an electrical instrument including a moving system comprising a movable element, a spiral spring, means attaching the inner end of the said spiral spring to the said movable element, a spring abutment-having a free end adjacent to and extending inl the direction of the outer end Lof the said spiral spring in` abuttingsideby-side relation therewith, the said spiral spring andabutment each having a generally rectangular-shaped crosssection with the abutment having a greater height than the spiral spring,l and meansconnecting the adjacent spring abutment and spiral spring together; the lastmentioned means comprising a helical-wound fastening spring turned onto the adjacent spring abutment and spiral spring.

2. The invention as#v recited in claim lfwherein the free end of the spring abutment'is tapered at the top and bottom edges thereof Vto a reduced height.

3. The invention as recited in claim ,2"Wherein the free end of the spiralsspring vextends; beyond the tapered end of the spring abutment..

4. The invention as recited in claim 1 including a bend formed in the saidfree end of the spring abutment, the helical Wound fastening spring terminating at one end thereof adjacent the said bend.

References Cited in the le of this patent UNITED STATES PATENTS 1,386,834 Beckert Aug.,9', 1921 1,501,698 Beckett July 15, 1924: 1,661,214 Carpenter .Mar, 6, 1928 1,708,900 Roller Apr. 9, 1929 2,656,204 Blomstrand Oct. 20, 1953 

